The status of the SARAF phase I linac

Leo Weissman

Soreq Nuclear Research CenterYavne, Israel

RuPAC 2012, September 2012

22

OutlineIntroduction SARAF Phase I

SARAF components performance/problemsECR ion source + LEBTRFQPrototype Superconducting Module (PSM)

Beam operations

Summary

33

SARAFSARAF – SSoreq AApplied RResearchAAccelerator FFacility

To enlarge the experimental nuclear science infrastructure and promote research in Israel

To develop and produce radioisotopes primarily for bio-medical applications

To modernize the source of neutrons at Soreq and extend neutron based research and applications

To create the field of modern accelerator technology in Israel

44

SARAF vision in 2006Phase I - 2006 Phase II – 2014

Phase I linac (excluding auxiliaries) was expected to be delivered as a turn-key by the industrial company, Research Instruments, former ACCEL.

Small local group will participate in the Phase I commissioning and willreceive adequate training from the industrial partner

Phase II built will be lunched after successful commissioning of Phase I

Phase II - 2010

LINAC 2006

CW 176 MHzDC

2 mA2 mA

55

SARAF today

EIS

LEBT RFQPSM

MEBTPhase I - 2012

D-plate

Beam line - 2012 targets

Beam dumps

Phase I operational, but not all specifications have been reached

Almost complete decoupling from the former industrial partners. Commissioning and operation by local team. Local team and its expertise has grown considerably

Experiments at the temporary beam line

Phase II is under intense discussion

6666

SARAF Phase I – Upstream View

EISLEBT

RFQMEBT

PSM

A. Nagler, Linac2006K. Dunkel, PAC 2007 C. Piel, PAC 2007 C. Piel, EPAC 2008 A. Nagler, Linac 2008J. Rodnizki, EPAC 2008J. Rodnizki, HB 2008 I. Mardor, PAC 2009A. Perry, SRF 2009

I. Mardor, SRF 2009L. Weissman, DIPAC 2009L. Weissman, Linac 2010J. Rodnizki, Linac 2010L. Weissman, RuPAC 2012

77

Temporary beam line

Targetstations

Beam dump

PSMD-plateVAT beam dump

Test station

88

ECR/LEBT

ECRIS8 mA p/d20 keV/uDC/pulsed

sol1

sol2

sol3

dipole

RFQ

beam blocker

aperture

wire/FC

slits

slow chopper

chopper beam blocker

new beam blocker/collimator

99

Radio Frequency Quadruple injector

Acceleration and bunching is performed by sophisticated modulation of the rods

4 rods structure traps and transportthe low-energy beam

RFQ works, but ….built by NTG

1010

0

50

100

150

200

250

300

0 10 20 30 40 50 60 70 80 90 100

Duty Cycle (%)

Forw

ard

RF

Pow

er (k

W)

18.11 20.11 23.11 26.11

8.12 9.12 20.12 22.12

23.12 24.12 31.12 Goal

Deuterons CW

Protons CW

RFQ conditioning

Stable operation of deuterons only at low DC(<10%)

1111

Insight into beam loss in RFQ

beam

det1

det2det3det4

det5

Beam transmission through RFQ 75-80% for 1 mA60-65% for 4 mA

Rate 2

RFQ power

Vacuum pressure

increase current

increase current

optimization LEBT

1212

Prototype Super conducting Module (PSM)Houses 6 x 176 MHz HWR (Half Wave Resonator) and 3 SC 6T Accelerates protons and deuterons from 1.5 MeV/u to 4 and 5 MeVVery compact design in longitudinal directionCavity vacuum and insulation vacuum separated

M. Pekeler, LINAC 2006

2500 mm

Beam

Routinely works with new 4 kW amplifiers

[I. Fishman et al.LINAC!2]

1313

HWR – parameters176 MHzFrequency0.09Geom. β

0.15 mLacc=βλ

5.5 MV/m840 kV

Eacc

Vacc

>4.7x108Q0@Eacc

~1.3x106

~130 HzQext

Loaded BW< 10 W @EmaxCryo load

The main goal of the Prototype cryomodule is demonstration ofacceleration of high current (> 1mA) CW proton(deuteron)beams to variable energy up to 4(5.5) MeV

1414

HWR Microphonics measurements ) 60 Hz/mbarHWRs are extremely sensitive to LHe pressure fluctuations (

Detuning signal is dominated by the Helium pressure drift

Detuning sometimes exceeds +/-200 Hz (~ +/-2 BW)

100 110 120 130 140 150 160 170 180 190 200-100

-80

-60

-40

-20

0

20

40

60

80

100

Time[Sec]

Freq

uenc

y D

etun

ing

[Hz]

Frequency Detuning

* Performed in collaboration with J.Delayen and K. Davis (JLab)

45 sec45 sec

1515

2011

Cavity BW

May 2012

Deterioration of piezo ranges

LV PZT HV PZT

beam axis

piezo tuner

stepping motor

1616

Cold window70OK

Copper strip tothermal shield for cooling

10-11 mbar4 0K

Temperaturesensor

Thermal shiled 50OK

RF couplers

10-7 mbar

1717

RF onRF off

RF on RF off

HWR1230 kV

HWR2460 kVHWR3

460 kV

HWR4720 kV

HWR5830 kV

HWR6425 kV

Coupler warming up during operation (set for 3.9 MeV)

Vacuum pressure

Warming couplers is the main limiting factor for the acceleration field values .The warming effect differs for different couplers

1818

Hydrogen diffusion along the accelerator

Significant increase of the hydrogen pressure after starting the ion source: hydrogen diffuses all way through the accelerator till the cryo module entrance

Opening the PSM valve slightly reduces hydrogen pressure: the cryomodule efficiently pumps hydrogen

We have to improve hydrogen pumping in EIS/LEBT area

An RGA was installed recently at the 1st MEBTchamber in order to verify the level theaccelerator contamination.

open EIS valve

open/close PSM valve

start RGA

H2O

H2

CO2O2

CO/N2

1919

The build up of hydrogen on the cryogenic surfaces at the entrance to the module.

During full or partial warm up intense hydrogen sublimation takes place at the temperatureshigher than 20 K.

Such massive sublimation and consequent absorption may result in redistribution of hydrogen

over more sensitive cryosurfaces of cavities which would lead todeterioration in cavity performance.

Hydrogen built up in cryomodule

temperaturebottom pipes

temperaturecavities

cavity vacuum

We plan to improve hydrogen pumping capacity in the region of EIS (powerful ark pump) and MEBT (new chamber&getter pump)

2020

Summary on Phase I status1. EIS/LEBT: preforms OK

Improve hydrogen pumping capacityBring chopper to routing operationBeam optics study

2. RFQ : major alignment problems were solved in 2010Return to conditioning campaign to achieve CW for deuteronsIf not successful consider major modification or even replacement

3. MEBT: introduction of beam scrapper improved beam operationImprove hydrogen pumping capacity

4. PSM: introduction new 4 kW RF amplifiers and new HVpiezo tuners improved performanceUnderstanding and improving the RF coupler performanceImproving the couplers cooling Stiffening cavities

2121

Beam optics study

Tune of the accelerator and the beam line is done with pulsed beam.Different diagnostics instrumentation used for tuning require different pulsed beams parameters (duty cycle and beam intensity).Furthermore when CW beam is operated its intensity varies within a factor ~100.

The questions asked by the accelerator users:How well does tune performed with pulsed beam work for CW beam?

How robust is a tune for the whole range of beam intensity (0.01-1 mA)?

How sensitive is a tune for variation of optics parameters in the front-end?

EIS

LEBT RFQPSM

MEBT

D-plate

Beam line targets

Beam dumps7 m

Phase I

2222

Phasing of the cavitiesTwo methods are used for phasing:

1.Non-destructive TOF that requires high beam intensity ~ 1 mA2.Destructive, Rutherford scattering (RS), which requires low intensity ~ a few μA

Two orders difference in the beam intensity; the results of TOF and RS are consistent within ~ 20 keV.

gold peak

For RS we had thick carbon backing whichallowed for measurement of two scattering peaks.

The main sources of systematic errors are error in energy calibration of the Si detector and uncertainties in the target thickness.

Carbon peak

RS spectrum

2323

Varying beam intensity by LEBT parameters

5 mm 10 mm 20 mm 30 mm 50 mm

Opening of the LEBT aperture is shown.

64 A 62 A

Use of a quartz viewer allows for fast study of influence of the front end parameters on the beam optics just before the target.

Varying the LEBT aperture and the LEBT 1st solenoid is used to vary the beam intensity within a factor 100. In the first order the beam position on target does not change with varying these parameters.

60 A 58 A

Changing current on the 1st LEBT solenoid.

2424

Experience with the Tungsten Beam dumpThe beam dump 50 micron Tungsten sheet fused to a water cooled cooper plate.Up to 10 MeV, no activation low neutron radiation is expected.

Visual inspection reveal strong blistering effectsBD #3 BD #4

After many hours of operation observe copper activation !

2525

Example of radioisotopes production

deuteron beam

Rh foilfilling ports

framemetal coolant

I. Silverman et al., NIM B261, 747-750 (2007)

103 Pd production via 103Rh(d,2n)103Pd reaction

26

Prototype capsule test

25 micron stainless steel foilcooled by liquid 1 mm metal NaK ,base cooled by waterMaximum ever applied power ~ 1 kWStable operation ~ 400 W

Ido Silverman et al

IR camera

Max 2150C

25 mm

25 μm SS + 1 mm NaK + 2 mm SS base

2727

fast valve

target

Vacuum protection

2828

Protons on Li target

Ethreshhold=1.88 MeV

7Li(p,n)7Be

Application of protons at ~ 1.92 MeV produce spectrumsimilar to a Maxwelian distribution at ~ kT=30 keV

This distribution mimics stellar neutron spectrum,and can be used for astrophysics research, as well as,for Boron Neutron Capture Therapy(BNCT)

M. Paul et al

2929

Liquid Li target (LILIT)Jet: 18 mm x 1.5 mm.Lithium velocity: 20 m/s.Wall assisted lithium jet

A. Arenshtam, D. Kijel et al

3030

LiF on water cooledcopper

G. Feinberg PhD thesis

gold foil

First tests: Solid Lithium Target

NaIscintillator

Neutrondosimeter

Neutronspectrometer

A. Kreisler

7Li(p,n)7Be

3131

n spectrum of d-Li with 40 MeV

M. Hagiwara et al. Fus. Sci. Tech., 48 (2005)

Other possible converters: Beryllium, Water, Heavy water

40 MeV, 250 mA Lithium Converter40 MeV, 250 mA Lithium Converter

40 MeV, 5 mA Graphite converter

40 MeV, 5 mA Graphite converter40 MeV , 5 mA Lithium Converter40 MeV , 5 mA Lithium Converter

4·1014 n/sec/mA

<En> = 15 MeV

3

3232

First experience with accelerated deuteronsWater flow

4.7 MeV10 μA d beam

Fast neutrons

150 μm LiF layer

109 n/secIsotropic distribution

Fast neutrons up to 20 MeV

109 n/secIsotropic distribution

Fast neutrons up to 20 MeV

T. Hirsh PhD. Thesis

3333

SummaryThere are still many problems at Phase I of

SARAF.The local team works hard to solve them.

Beam operation in 2011-12 showed that SARAF even at Phase I has potential to become an user facility with broad scope of the applications

Conceptual design of Phase II is done

3434

Phase II,ANL conceptual design (2012)

The ion source and LEBT are in the original positionNew (RFQ) MEBT and superconducting linac176 MHz β=0.09 and β=0.16 Half Wave ResonatorsTotal superconducting linac = 19.47 m7 low-β HWR operating at 1 MV and 21 high-β HWR operating at 2 MV

– Beam dynamics study at [B. Mustapha et al. IPAC12, J. Rodnizki et al. LINAC12]

Total (static and dynamic) power dissipation ~ 350 W @4KP. Ostroumov et al. LINAC12

3535

People involved in accelerator &experiments(including students, consulters and partially affiliated personal ) :

D. Berkovits, A. Arenshtam, Y. Ben-Aliz, Y. Buzaglo, O. Dudovich,Y. Eisen, I. Eliyahu, G. Finberg, I. Fishman,

I. Gavish, I. Gertz, A. Grin, S. Halfon, D. Har-Even, Y. Haruvi,D. Hirshman, T. Hirsh, T. Horovits, B. Keizer, A. Kreisel,

D. Kijel, G. Lempert, Y. Luner, A. Perry, E. Reinfeld, J.Rodnizki, G. Shimel, A. Shor, I. Silverman, E. Zemach, L. Weissman.

Phase I commissioning,accelerator operation,maintenance of the accelerator,maintenance beam line, maintenance the infrastructure,users support, preparation to Phase II

~ 20 persons

3636

Temporary beam line

3737

Quality of electricity

Funds for upgrade of the facility UPS.New UPS operational in early 2013

3838

Some slides

3939

Beam operation of Phase I. Temporary beam line.

fast valve

wire profilestargets

VAT BD

4-jawscollimators

Tungsten BDdiagnostic crossdipoles

quadruples

steers

Very strong demand for the beam time

Some research can be done only at Phase I energies during the time window before the Phase II installation.

4040

Developments on the BD line

A. Grin

GANILRGM

GANILwire profiler

Linear motion manipulator &load-lock chamber

A. GrinL. Weissman

4141

s-only

64

76

70

80 82

86 87 88

He-burning stage:13C(α,n)16O

22Ne(α,n)25MgT≈350 MK

~ 30 keV

SrnSr 9190 ),( γG. Feinberg PhD thesis

4242

Big Bang Li production problem

Measure destruction rate of 7Be via the 7Be(n,α)α reaction

M. Gai et al

4343

n

n

n

n

nα

Li

B10

B10

B10B10

B10

B10B10 B10

B10 B10

B10

B10B10

~ 109 10B atomsin cell

Boron Neutron Capture Therapy

Locher G. L., Biological effects and therapeutic possibilities of neutrons, Am. J. Roentgenol, 36, 1-13, 1936.

1. Selectively deliver 10B to the tumor cells. 2. Irradiate the target region with neutrons. 3. The short range of the 10B(n,α)7Li reaction product, 5-8 μm in tissue, restrict the dose to the boron loaded area.

4444

Boron Neutron Capture Therapy

Sh. Halfon PhD. Thesis

4545

MEBT/PSM valve

Natural PSM warm upwithout pumpingRFQ/MEBT is pumped

RFQ/MEBT is vented

RFQ/MEBT ispumped

Leak rate through the valve is ~ 3 10-6 l mbar/s when RFQ is ventedAs the consequence RFQ has to be pumped while the PSM is cold

4646

Replacement of vacuum flanges

Several times vacuum failure occurs during conditioning

Damaged vacuum or water o-rings, signs on flunges

D. Rubin, G. Lampert

474747

Helium processing :

99.9999% purity, 4 10-5 mbar

up to 43 MV/m 10% DC

0.01

0.1

1

10

100

1000

15 20 25 30 35

Epeak (MV/m)

Rad

iatio

n (m

R/h

) HWR1

HWR2

HWR3HWR4

HWR5

HWR6

0.01

0.1

1

10

100

1000

15 20 25 30 35

Epeak (MV/m)

Rad

iatio

n (m

R/h

)HWR1

HWR2

HWR3

HWR4

HWR5

HWR6

Before

After

He processing

A. Perry et al, SRF2009

nominal peak field

48

4 kW RF power supplies

I. Fishman, Tuesday discussion

49

Cavity Acceleration voltage (kV)

Phase(deg)

Energy(MeV)

HWR 1 213 -90 1.536HWR 2 0 0 1.536HWR 3 646 -10 2.003HWR 4 493 -15 2.416HWR 5 697 -35 2.971HWR 6 544 10- 3.501

Cavity Acceleration )voltage (kV

Phase(deg)

Energy (MeV)

HWR 1 212 -95 1.5HWR 2 552 30 1.86HWR 3 646 -25 2.36HWR 4 493 -10 2.81HWR 5 552 -10 3.31HWR 6 544 -20 3.82

Accelerator tunes

from Arik Kreisel

Type 1 Type 2

HWR6HWR5

HWR6

HWR4

HWR3

HWR1HWR2

5050

Emittance 3.7 MeV

515151

LEBT aperture

-19 -4 11-30

-5

21

x [mm]

x' [mrad]

50 mm

-19 -4 11-30

-5

21

x [mm]

x' [mrad]

5 mm

-19 -4 11-30

-5

21

x [mm]

x' [mrad]

25 mm

-19 -4 11-30

-5

21

x [mm]

x' [mrad]

15 mm

-19 -4 11-30

-5

21

x [mm]

x' [mrad]

10 mm

Manipulating beam size, current and emittance using the LEBT aperture

0

0.05

0.1

0.15

0.2

0.25

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

LEBT current(mA)

()

50

55

60

65

70

75

80

85

RMS norm emiTransmission

π

Aperture diameter (mm)5 10 15 20 25 50

norm

rm

s em

it (

mm

mra

d)

Tra

nsm

issi

on (%

)

5252

2500 mm

Beam

M. Pekeler, LINAC 2006

SC solenoid current lead leak

5

Isolation feed through -heat

damage

He hose for cooling

Current supply

5353

Beam Dynamics

HWR1 entrance: First cavity is used as a buncher.

HWR1 exit: Forward protons are now less energetic.

HWR2 entrerance: Only 5 cm drift from HWR1. Forward protons are still less energetic.

HWR2 exit: In order to accelerate without increasing ΔE, it is necessary to work at a positive phase in HWR2.

ComponentAcceleration voltage kV

PhaseEnergy MeV

HWR 1 229 -90 1.52

HWR 2 459 30 1.81

HWR 3 459 -30 2.14

HWR 4 722 -20 2.76

HWR 5 833 -20 3.52

HWR 6 425 -10 3.93

Protons 0.2 mA

53

Longitudinal phase space

5454

Projectile in target power density

54

1 m

55555

PSM cooling processNatural warm up (10K/hour)

24 h

K

0

270

12 h

K

135

265

3 h

K

0

210

Keeping this procedure, we never recognized a Q-disease effect, although, the cavities were

NOT pre-baked in the fabrication

Fast cool down (>270K/hour)Slow cool down (30K/hour)

5656

Acceleration of chopped beam

chopperdump

VATdump

D-plateFC

MEBTBPM

D-plateFFC

MEBTBPM

EIS

LEBTRFQ

PSM

MEBT D-plate VAT BD

BPMFC

FFCchopper

chopperBD

The next steps:Integration of the chopper into machine safety Beam studiesRouting use

5757

HWR3

HWR6

HWR5

HWR4

HWR2

Coupler warming up, dependence on beam current

RF on RF on

CW beam1 mA

Warming rate changes while operating intense current (especially coupler #3)Understanding of the coupler warming and improvement in their performanceis in progress

beam on

5858

MEBT beam blocker/collimator

A. Grin

H2

During beam operation the collimator cuts the tails of the beam (~few %) which improves the stability of the cavity operation). The scrapped protons diffuse from collimator surface which leads to increase of the hydrogen partial pressure during beam operation. It is likely that the most of that hydrogen molecules end up on the cryo surfaces at the entrance of the module.We have to improve pumping speed in MEBT area